DESCRIPTION (Abstract of the Core) This core, which was a part of the Molecular Pathobiology Core during the last funding period, has been reorganized to serve as a repository of tissues and provide expertise and facilities in areas of histology, immunohistochemistry, in situ hybridization and electron microspcopy. It is stated that because of increase in volume of work and sophistication of technologies, the members (Drs. Evers, Greeley Jr., Townsend and Cooper) of this Program Project has decided to create this Histopathology Core. Service provide by this core will be utilized by all members of this Program Project. In general, this core laboratory will provide the analytic facility as well as the necessary instruments to perform and assist in the following studies: (1) assessment of structural integrity of organs and tissues for functional properties, (2) assessment of structural alterations induced by modulating agents, (3) comparative assessment of xenografts and tumors, (4) assessment of differentiaton, de-novo and induced, and of cultured cells, (5) assessment of purity/homogeneity of isolated cell fractions as well as of organs, (6) characterization of polyclonal and monoclonal antibodies, (7) immunolocalization studies, (8) gene expression and localization, and lastly (9) experiments involving cell proliferation and cell death kinetics. It is anticipated that utilization of this core will greatly facilitate the overall activity of the Program Project.